Turbine engine airfoils must perform under conditions of high stresses and dynamic excitations. Where airfoils are grouped, such as in a rotor, individual frequency responses can interact and reinforce each other to create undue stresses on the rotor, when successive blades have the same critical frequency ranges. Mistuning, the design of periodically different airfoils to achieve different frequencies, has been traditionally accomplished by selecting blades having different shapes within the same rotor.